Equation of state and heavy-quark free energy at finite temperature and density in two flavor lattice QCD with Wilson quark action

Abstract

We study the equation of state at finite temperature and density in two-flavor QCD with the RGimproved gluon action and the clover-improved Wilson quark action on a 16 3 × 4 lattice. Along the lines of constant physics at mPS/mV = 0.65 and 0.80, we compute the second and forth derivatives of the grand canonical partition function with respect to the quark chemical potential µq = (µu +µ d )/2 and the isospin chemical potential µI = (µu − µ d )/2 at vanishing chemical potentials, and study the behaviors of thermodynamic quantities at finite µq using these derivatives for the case µI = 0. In particular, we study density fluctuations at nonezero temperature and density by calculating the quark number and isospin susceptibilities and their derivatives with respect to µq. To suppress statistical fluctuations, we also examine new techniques applicable at low densities. We find a large enhancement in the fluctuation of quark number when the density increased near the pseudocritical temperature, suggesting a critical point at finite µq terminating the first order transition line between hadronic and quark gluon plasma phases. This result agrees with the previous results using staggered-type quark actions qualitatively. Furthermore, we study heavy-quark free energies and Debye screening masses at finite density by measuring the first and second derivatives of these quantities for various color channels of heavy quark-quark and quark-anti-quark pairs. The results suggest that, to the leading order of µq, the interaction between two quarks becomes stronger at finite densities, while that between quark and anti-quark becomes weaker.

The phase diagram of dense QCD

“…In the latter case, extremely precise determination of ρ(θ) and O θ is crucially important. So far, the density of states method is applied for relatively small values of µ q /T combined with the Taylor expansion of the fermion determinant [128,136].…”

Hadron properties at finite temperature and density with two-flavors of Wilson fermion

“…Therefore, it is important to compare these two screening masses. The gluon screening-mass (so called Debye screening mass) has been studied from the Polyakov-line correlator based on the Taylor expansion method using the same gauge configurations [2,3]. The Debye screening mass is also expressed as power series ofμ, /T ), respectively.…”

“…We utilize the gauge configurations generated by WHOT-QCD Collaboration on 16 3 × 4 lattice with the renormalization-group improved Iwasaki gauge action and N f = 2 clover-improved Wilson quark action [2,3] Fig. 1(b).…”

“…In this article, we focus on screening masses of mesons in pseudo-scalar (PS) and vector (V) channels calculated from the spatial correlation functions, and present current results of our group in lattice QCD simulations with two flavors of the Wilson-type quark action. Using gauge configurations generated by WHOT-QCD Collaboration [2,3], we calculate the meson correlation functions along the line of constant physics and extract temperature dependence of the meson screening-masses from long spatial-distance behavior of the correlators.…”

Scaling behavior of chiral phase transition in two-flavor QCD with improved Wilson quarks at finite density

“…The critical exponents have the values 1/y ≡ 1/(β δ ) = 0.537(7) and 1/δ = 0.2061 (9), and f (x) is the scaling function. In 2-flavor QCD, we identify M ∼ ψψ , h ∼ 2m q a and t ∼ β − β ct .…”